You might consider not portraying it as a fight. One does not overcome sadness with violence. And you overcome loneliness by making friends, not by beating them up.
If you do not do another 1 bit color you might want to portrait your dark more like a cold and gloomy thing and the light as warmth with your color scheme. It is too easy to equate dark with evil and light with good. But your theme does not sound like such a conflict. More like spring excorcising winter. It is an obstacle, a condition to overcome, not winning against an adversary. Of course you can go full abstract and fight the dark stuff.
Your bird hero could return stolen eggs to the commoners as an alternative to fighting ;-)
Oh and a tiny advice. You should think about releasing demo versions of your games along with the paid version. This is itch and not steam. People can not easily give back the game, if it is not what they expected and they cannot read any public reviews.